1. Field of the Invention
The present invention relates to pins which may be inserted in a medullary cavity by a surgeon to increase the strength of a bone while healing and provide additional strength to the bone after it has healed.
2. Description of the Prior Art
Various intermedullary pins have been used in the past by surgeons to enhance the strength of a fractured bone both during the healing process and after the completion of the healing process. Among these well-known pins the solid non-expanding pin, examples of which may be found in U.S. Pat. No. 2,675,801, issued Apr. 20, 1964, to Bambara, which discloses a solid intermedullary pin comprising a rod shaped member having a substantially cruciform cross section. U.S. Pat. No. 2,998,007, issued Aug. 29, 1961, to Herzog shows an internal tubular splint which extends through the fractured bone and has longitudinal slots through its center. The splint itself is solid except for the slots, and pins are provided for insertion into the slots for holding the splint in place in the bone itself. U.S. Pat. No. 3,717,146, issued Feb. 20, 1973, to Halloran, shows a solid intramedullary pin with threaded ends for engagement with the separated bone halves to secure the pin to the bone for compression stabilization.
Expanding pins for use in the medullary cavity of a fractured bone have also been conceived in the prior art. For example, U.S. Pat. No. 2,672,861, issued Mar. 23, 1954, to Jonas et al, shows an intermedullary pin having a base and a telescoping pin portion wherein the pin is forced from the base by a spring member which is contained within the base. This device has certain inherent disadvantages including the fact that the constant pressure created by the spring has been believed to cause pressure necrosis within the medullary cavity. U.S. Pat. No. 4,016,874, issued Apr. 12, 1977, to Maffei et al, discloses a three-part bone-setting spline pin. The device has two tubular outer members which are screwed into the two halves of the fractured bone. The third member comprises a rod which is inserted into each of the outer members to hold them in proper alignment.